import math

x, y, X, Y = [float(i) for i in input().split()]
print(math.sqrt((x-X)**2 + abs(y-Y)**2)) import math math float(i) for i in input().split() for i in input().split() i input().split() ().split () input split for i in input().split() float(i) float i x, y, X, Y = [float(i) for i in input().split()] x [float(i) for i in input().split()] y X Y print(math.sqrt((x-X)**2 + abs(y-Y)**2)) print math.sqrt((x-X)**2 + abs(y-Y)**2) math.sqrt math sqrt (x-X)**2 + abs(y-Y)**2 (x-X)**2 x-X x X 2 abs(y-Y)**2 abs(y-Y) abs y-Y y Y 2 Y = [float(i) for i in input().split()] [float(i) for i in input().split()] Y y, X, Y = [float(i) for i in input().split()] [float(i) for i in input().split()] y x, y, X, Y = [float(i) for i in input().split()] [float(i) for i in input().split()] x X, Y = [float(i) for i in input().split()] [float(i) for i in input().split()] X
import math

x, y, X, Y = [float(i) for i in input().split()]
print(math.sqrt((x-X)**2 + abs(y-Y)**2))